Filled resins, e.g., glass fiber and fabric reinforced resins, are well-known as suitable materials for forming structural units in the aircraft and other industries. A wide variety of resins have been proposed in the past for formulating such structures and as laminating resins for joining various materials. For example, polyester, epoxy and polycarbonate resins have been utilized as matrix resins for glass fiber-resin laminates. One of the difficulties experienced in the use of these resins, however, is that they are difficult to mold and mechanically work. Thus, it is often necessary to apply the resin in liquid form to the glass fibers or substrate to be laminated and then solidify the composite in order to obtain a suitable product. The resins previously used have to be melted or dissolved in a suitable solvent in order to achieve the desired liquid form. Many of these resins, however, decompose or suffer some deleterious chemical change when heated to temperatures sufficiently high to achieve melting. The result is a laminate or reinforced resin with reduced strength and physical properties.
Moreover, many of the previously used resins are insoluble in conventional volatile solvents. In addition, when forming laminates with solvent solutions of resins, it is necessary to employ special means for driving off and collecting those solvents which are capable of dissolving the resins but are relatively non-volatile.
In addition, the prior art matrix and laminating resins do not possess a sufficiently high degree of thermal stability which is requisite in many industrial applications.
It has been heretofore proposed to provide low melting laminating polymers. These polymers may be melted at low temperatures, contacted with the filler material or substrate to be laminated and cured or cross-linked to the resinous state. A serious disadvantage associated with these low-melting polymers, however, is that cross-linking involves a chemical reaction which liberates a volatile by-product such as carbon dioxide or water. The liberation of these reaction products operates to form voids in the resulting product. Obviously, the prior art low-melting laminating polymers may not be used in applications requiring close tolerance or uniform compositions throughout.
It is an object of the invention to provide low-melting polymers which may easily be admixed with fillers or contacted with substrates to be laminated and cross-linked to form a firmly bonded article having a uniform composition throughout.
It is a further object of the invention to provide novel reinforced and laminated resin compositions having high degrees of strength and thermal stability.
It is another object to provide low-melting polymers which may be cross-linked without the production of volatile materials.